Method for detecting control information in wireless communication system

ABSTRACT

A method for detecting control information in a wireless communication system is provided. The method includes checking a cyclic redundancy check (CRC) error by monitoring control channels, determining whether a value of an error check field is equal to a specific value, and, if the value of the error check field is equal to a specific value, detecting the control information on the control channel.

This application is a continuation of U.S. application Ser. No.12/680,482 filed Mar. 26, 2010 which is a 35 U.S.C. §371 National Stateentry of International Application No. PCT/KR2008/005178 filed Sep. 26,2008, and claims priority to U.S. Provisional Application No. 60/976,140filed Sep. 28, 2007 and 61/095,287 filed Sep. 8, 2008, each of which ishereby incorporated by reference in its entirety as if fully set forthherein.

TECHNICAL FIELD

The present invention relates to wireless communications, and moreparticularly, to a method for detecting control information in awireless communication system.

BACKGROUND ART

In a wireless communication system, a base station (BS) generallyprovides services to a plurality of user equipments (UEs). The BSschedules user data for the plurality of UEs, and transmits controlinformation together with the user data. The control informationcontains scheduling information for the user data. A channel forcarrying the control information is generally referred to as a controlchannel. A channel for carrying the user data is generally referred toas a data channel. The UE monitors the control channel to search controlinformation of the UE, and processes data of the UE by using the controlinformation.

In order for the UE to receive the user data allocated to the UE, thecontrol information for the user data on the control channel must bereceived. In general, a plurality of pieces of control information ofthe plurality of UEs are multiplexed within one transmission interval inan assigned bandwidth. That is, to provide a service to the plurality ofUEs, the BS multiplexes the plurality of pieces of control informationof the plurality of UEs and transmits the control information on aplurality of control channels. Each UE searchs its own control channelamong the plurality of control channels.

Blind detection is one of schemes for detecting specific controlinformation among a plurality of pieces of multiplexed controlinformation. The blind detection implies attempting by the UE to recovera control channel by combining a plurality of pieces of information in astate where information required to recover the control channel does notexist. That is, in a state where the UE neither knows whether aplurality of pieces of control information received from the BS iscontrol information of the UE nor knows in which location the controlinformation of the UE exists, the UE decodes all pieces of providedcontrol information until the control information of the UE is detected.The UE may use its unique information to determine whether the receivedcontrol information is control information of the UE. For example, whenthe BS multiplexes control information of each UE, the BS may transmit aunique identifier of each UE by masking the identifier onto a cyclicredundancy check (CRC). The CRC is a code used in error detection. TheUE demasks its unique identifier to the CRC of the received controlinformation, and thereafter can determine whether the received controlinformation is control information of the UE by performing CRC checking.

However, when the UE monitors the control channel through CRC errordetection, even if the control channel is a control channel of anotherUE, the CRC error may not be detected and thus a decoding result may beerroneously informed that decoding is successful. In case ofsemi-persistent scheduling (SPS), incorrect CRC error detection becomesmore problematic. This is because, in the SPS, the UE receives controlinformation for allocating radio resources and thereafter transmits orreceives data by using the radio resources allocated using the controlinformation during an SPS interval. This results in waste of limitedradio resources and deterioration in reliability of wirelesscommunication. Accordingly, there is a need for a method for detectingcontrol information with an increased accuracy.

DISCLOSURE OF INVENTION Technical Problem

The present invention provides a method for detecting controlinformation in a wireless communication system.

Technical Solution

In one aspect, a method for detecting control information in a wirelesscommunication system is provided. The method includes checking a cyclicredundancy check (CRC) error by monitoring control channels, determiningwhether a value of an error check field is equal to a specific value,where the error check field is a field among fields included in thecontrol information on a control channel, the control channel in whichthe CRC error is not detected, and, if the value of the error checkfield is equal to the specific value, detecting the control informationon the control channel, the control channel in which the CRC error isnot detected.

In another aspect, a user equipment is provided. The user equipmentincludes a radio frequency (RF) unit for transmitting and receiving aradio signal and a processor coupled with the RF unit and configured tocheck a CRC error by monitoring control channels, determine whether avalue of an error check field is equal to a specific value, where theerror check field is a field among fields included in the controlinformation on a control channel, the control channel in which the CRCerror is not detected, and, if the value of the error check field isequal to the specific value, detect the control information on thecontrol channel, the control channel in which the CRC error is notdetected.

In still another aspect, a method for transmitting control informationin a wireless communication system is provided. The method includesgenerating the control information comprising an error check fieldhaving a specific value and transmitting the control information on acontrol channel by appending a CRC to the control information, wherein asuccessful reception of the control information is determined accordingto the specific value of the error check field and the CRC.

Advantageous Effects

A method for detecting control information can be provided with anincreased accuracy in a wireless communication system. A specific valueof an error check field can be used as a virtual cyclic redundancy check(CRC). A user equipment can increase an accuracy of CRC error checkingby using the virtual CRC when detecting the control information. Thatis, the control information can be accurately detected while effectivelyutilizing radio resources. Therefore, an overall system performance canbe increased.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a wireless communication system.

FIG. 2 is a block diagram showing functional split between an evolveduniversal terrestrial radio access network (E-UTRAN) and an evolvedpacket core (EPC).

FIG. 3 is a block diagram showing constitutional elements of a userequipment.

FIG. 4 is a diagram showing a radio protocol architecture for a userplane.

FIG. 5 is a diagram showing a radio protocol architecture for a controlplane.

FIG. 6 shows mapping between downlink logical channels and downlinktransport channels.

FIG. 7 shows mapping between downlink transport channels and downlinkphysical channels.

FIG. 8 shows a structure of a radio frame.

FIG. 9 shows an example of a resource grid for one downlink slot.

FIG. 10 shows a structure of a subframe.

FIG. 11 is a flowchart showing a physical downlink control channel(PDCCH) configuration.

FIG. 12 is a flowchart showing PDCCH processing.

FIG. 13 shows an example of a method for utilizing an unused informationfield among a plurality of information fields constituting a downlinkcontrol information (DCI) format.

FIG. 14 is a flowchart showing a method for detecting controlinformation according to an embodiment of the present invention.

FIG. 15 is a flow diagram showing downlink data transmission using adynamic scheduling scheme.

FIG. 16 is a flow diagram showing uplink data transmission using adynamic scheduling scheme.

FIG. 17 shows an example of a traffic model in a voice over Internetprotocol (VoIP).

FIG. 18 is a flow diagram showing downlink data transmission using asemi-persistent scheduling scheme.

FIG. 19 is a flow diagram showing uplink data transmission using asemi-persistent scheduling scheme.

MODE FOR THE INVENTION

FIG. 1 is a block diagram showing a wireless communication system. Thewireless communication system may have a network structure of anevolved-universal mobile telecommunications system (E-UMTS). The E-UMTSmay be referred to as a long-term evolution (LTE) system. The wirelesscommunication system can be widely deployed to provide a variety ofcommunication services, such as voices, packet data, etc.

Referring to FIG. 1, an evolved-UMTS terrestrial radio access network(E-UTRAN) includes at least one base station (BS) 20 which provides acontrol plane and a user plane.

A user equipment (UE) 10 may be fixed or mobile, and may be referred toas another terminology, such as a mobile station (MS), a user terminal(UT), a subscriber station (SS), a wireless device, etc. The BS 20 isgenerally a fixed station that communicates with the UE 10 and may bereferred to as another terminology, such as an evolved node-B (eNB), abase transceiver system (BTS), an access point, etc. The BS 20 canprovide services to one or more cells. The cell is an area where the BS20 provides communication services. Interfaces for transmitting usertraffic or control traffic may be used between the BSs 20. Hereinafter,a downlink is defined as a communication link from the BS 20 to the UE10, and an uplink is defined as a communication link from the UE 10 tothe BS 20.

The BSs 20 are interconnected by means of an X2 interface. The BSs 20are also connected by means of an S1 interface to an evolved packet core(EPC), more specifically, to a mobility management entity (MME)/servinggateway (S-GW) 30. The S1 interface supports a many-to-many relationbetween the BS 20 and the MME/S-GW 30.

The wireless communication system may be not only a multiple inputmultiple output (MIMO) system or a multiple input single output (MISO)system but also a single input single output (SISO) system or a singleinput multiple output (SIMO) system. A MIMO scheme uses multipletransmit (Tx) antennas and multiple receive (Rx) antennas to improvedata Tx/Rx efficiency and spectral efficiency. Examples of the MIMOscheme include spatial diversity, spatial multiplexing, beamforming,etc.

FIG. 2 is a block diagram showing functional split between the E-UTRANand the EPC. Slashed boxes depict radio protocol layers and white boxesdepict the functional entities of the control plane.

Referring to FIG. 2, the BS performs the following functions: (1)functions for radio resource management (RRM) such as radio bearercontrol, radio admission control, connection mobility control, anddynamic allocation of resources to the UE, (2) Internet protocol (IP)header compression and encryption of user data streams, (3) routing ofuser plane data to the S-GW, (4) scheduling and transmission of pagingmessages, (5) scheduling and transmission of broadcast information and(6) measurement and measurement reporting configuration for mobility andscheduling.

The MME performs the following functions: (1) non-access stratum (NAS)signaling, (2) NAS signaling security, (3) idle mode UE reachability,(4) tracking area list management, (5) roaming and (6) authentication.

The S-GW performs the following functions: (1) mobility anchoring and(2) lawful interception. A PDN gateway (P-GW) performs the followingfunctions: (1) UE Internet protocol (IP) allocation and (2) packetfiltering.

FIG. 3 is a block diagram showing constitutional elements of the UE. AUE 50 includes a processor 51, a memory 52, a radio frequency (RF) unit53, a display unit 54, and a user interface unit 55. Layers of the radiointerface protocol are implemented in the processor 51. The processor 51provides the control plane and the user plane. The function of eachlayer can be implemented in the processor 51. The memory 52 is coupledto the processor 51 and stores an operating system, applications, andgeneral files. The display unit 54 displays a variety of information ofthe UE and may use a well-known element such as a liquid crystal display(LCD), an organic light emitting diode (OLED), etc. The user interfaceunit 55 can be configured with a combination of well-known userinterfaces such as a keypad, a touch screen, etc. The RF unit 53 iscoupled to the processor 51 and transmits and/or receives radio signals.

Layers of a radio interface protocol between the UE and the network canbe classified into L1 layer (a first layer), L2 layer (a second layer),and L3 layer (a third layer) based on the lower three layers of the opensystem interconnection (OSI) model that is well-known in thecommunication system. A physical layer, or simply a PHY layer, belongsto the first layer and provides an information transfer service througha physical channel. A radio resource control (RRC) layer belongs to thethird layer and serves to control radio resources between the UE and thenetwork. The UE and the network exchange RRC messages via the RRC layer.

FIG. 4 is a diagram showing a radio protocol architecture for the userplane. FIG. 5 is a diagram showing a radio protocol architecture for thecontrol plane. They illustrate the architecture of a radio interfaceprotocol between the UE and the E-UTRAN. The user plane is a protocolstack for user data transmission. The control plane is a protocol stackfor control signal transmission.

Referring to FIGS. 4 and 5, a PHY layer belongs to the first layer andprovides an upper layer with an information transfer service through aphysical channel. The PHY layer is coupled with a medium access control(MAC) layer, i.e., an upper layer of the PHY layer, through a transportchannel. Data is transferred between the MAC layer and the PHY layerthrough the transport channel. Between different PHY layers (i.e., a PHYlayer of a transmitter and a PHY layer of a receiver), data istransferred through the physical channel.

The MAC layer belongs to the second layer and provides services to aradio link control (RLC) layer, i.e., an upper layer of the MAC layer,through a logical channel. The RLC layer in the second layer supportsreliable data transfer. There are three operating modes in the RLClayer, that is, a transparent mode (TM), an unacknowledged mode (UM),and an acknowledged mode (AM) according to a data transfer method. An AMRLC provides bidirectional data transmission services and supportsretransmission when the transfer of the RLC protocol data unit (PDU)fails.

A packet data convergence protocol (PDCP) layer belongs to the secondlayer and performs a header compression function for reducing an IPpacket header size.

A radio resource control (RRC) layer belongs to the third layer and isdefined only in the control plane. The RRC layer serves to control thelogical channel, the transport channel, and the physical channel inassociation with configuration, reconfiguration and release of radiobearers (RBs). An RB is a service provided by the second layer for datatransmission between the UE and the E-UTRAN. When an RRC connection isestablished between an RRC layer of the UE and an RRC layer of thenetwork, it is called that the UE is in an RRC connected mode. When theRRC connection is not established yet, it is called that the UE is in anRRC idle mode.

A non-access stratum (NAS) layer belongs to an upper layer of the RRClayer and serves to perform session management, mobility management, orthe like.

FIG. 6 shows mapping between downlink logical channels and downlinktransport channels. This may be found in section 6.1.3.2 of the 3GPP TS36.300 V8.3.0 (2007-12) Technical Specification Group Radio AccessNetwork; Evolved Universal Terrestrial Radio Access (E-UTRA) and EvolvedUniversal Terrestrial Radio Access Network (E-UTRAN); Overalldescription; Stage 2 (Release 8).

Referring to FIG. 6, a paging control channel (PCCH) is mapped to apaging channel (PCH). A broadcast control channel (BCCH) is mapped to abroadcast channel (BCH) or a downlink shared channel (DL-SCH). A commoncontrol channel (CCCH), a dedicated control channel (DCCH), a dedicatedtraffic channel (DTCH), a multicast control channel (MCCH), and amulticast traffic channel (MTCH) are mapped to the DL-SCH. The MCCH andMTCH are also mapped to a multicast channel (MCH).

A type of each logical channel is defined according to a type ofinformation to be transmitted. A logical channel is classified into twogroups, i.e., a control channel and a traffic channel.

The control channel is used for the transfer of control planeinformation. The BCCH is a downlink channel for broadcasting systemcontrol information. The PCCH is a downlink channel for transmittingpaging information and is used when a network does not know the locationof a UE. The CCCH is a channel for transmitting control informationbetween the UE and the network and is used when there is no RRCconnection established between the UE and the network. The MCCH is apoint-to-multipoint downlink channel used for transmitting multimediabroadcast multicast service (MBMS) control information. The MCCH is usedby UEs that receive an MBMS. The DCCH is a point-to-pointuni-directional channel for transmitting dedicated control informationbetween the UE and the network, and is used by UEs having an RRCconnection.

The traffic channel is used for the transfer of user plane information.The DTCH is a point-to-point channel used for the transfer of userinformation. The DTCH can exist in both uplink and downlink. The MTCH isa point-to-multipoint downlink channel for transmitting traffic data andis used by the UEs that receive the MBMS.

The transport channel is classified according to a type andcharacteristic of data transmission through a radio interface. The BCHis broadcast in the entire coverage area of the cell and has a fixed,pre-defined transport format. The DL-SCH is characterized by support forhybrid automatic repeat request (HARM), support for dynamic linkadaptation by varying modulation, coding, and Tx power, possibility tobe broadcast in the entire cell, and possibility to use beamforming,support for both dynamic and semi-static resource allocation, supportfor UE discontinuous reception (DRX) to enable UE power saving, andsupport for MBMS transmission. The PCH is characterized by support forDRX to enable UE power saving and support for broadcast in the entirecoverage area of the cell. The MCH is characterized by support forbroadcast in the entire coverage area of the cell and support for anMBMS single frequency network (MBSFN).

FIG. 7 shows mapping between downlink transport channels and downlinkphysical channels. This may be found in section 5.3.1 of the 3GPP TS36.300 V8.3.0 (2007-12).

Referring to FIG. 7, a BCH is mapped to a physical broadcast channel(PBCH). An MCH is mapped to a physical multicast channel (PMCH). A PCHand a DL-SCH are mapped to a physical downlink shared channel (PDSCH).The PBCH carries a BCH transport block. The PMCH carries the MCH. ThePDSCH carries the DL-SCH and the PCH.

There are several downlink physical control channels used in a PHYlayer. A physical downlink control channel (PDCCH) informs a UE ofresource allocation of the PCH and DL-SCH, and also informs the UE ofHARQ information related to the DL-SCH. The PDCCH may carry an uplinkscheduling grant which informs the UE of resource allocation for uplinktransmission. A physical control format indicator channel (PCFICH)informs the UE of the number of orthogonal frequency divisionmultiplexing (OFDM) symbols used for the transfer of PDCCHs in asubframe. The PCFICH is transmitted in every subframe. A physical hybridARQ indicator channel (PHICH) carries HARQ acknowledgement(ACK)/negative-acknowledgement (NACK) signals in response to uplinktransmission.

FIG. 8 shows a structure of a radio frame.

Referring to FIG. 8, the radio frame includes 10 subframes. One subframeincludes two slots. A time for transmitting one subframe is defined as atransmission time interval (TTI). For example, one subframe may have alength of 1 ms, and one slot may have a length of 0.5 ms.

The radio frame of FIG. 8 is shown for exemplary purposes only. Thus,the number of subframes included in the radio frame or the number ofslots included in the subframe or the number of OFDM symbols included inthe slot may change variously.

FIG. 9 shows an example of a resource grid for one downlink slot.

Referring to FIG. 9, the downlink slot includes a plurality of OFDMsymbols in a time domain. Although it is described herein that onedownlink slot includes 7 OFDM symbols and one resource block includes 12subcarriers in a frequency domain, this is for exemplary purposes only,and thus the number of OFDM symbols and the number of subcarriers arenot limited thereto.

Elements on the resource grid are referred to as resource elements. Oneresource block includes 12×7 resource elements. The number of resourceblocks included in the downlink slot NDL depends on a downlinktransmission bandwidth determined in a cell.

FIG. 10 shows a structure of a subframe.

Referring to FIG. 10, the subframe includes two consecutive slots. Amaximum of three OFDM symbols located in a front portion of a 1st slotwithin the subframe correspond to a control region to be assigned with aPDCCH. The remaining OFDM symbols correspond to a data region to beassigned with a PDSCH. In addition to the PDCCH, control channels suchas a PCFICH, a PHICH, etc., can be assigned to the control region. TheUE can read data information transmitted through the PDSCH by decodingcontrol information transmitted through the PDCCH. Although the controlregion includes three OFDM symbols herein, this is for exemplarypurposes only. The number of OFDM symbols included in the control regionof the subframe can be known by the PCFICH.

The control region consists of a plurality of control channel elements(CCEs) that is a logical CCE sequence. Hereinafter, the CCE sequencedenotes an aggregation of all CCEs constituting the control region inone subframe. The CCE corresponds to a plurality of resource elementgroups. For example, the CCE may correspond to 9 resource elementgroups. The resource element group is used to define mapping of acontrol channel onto a resource element. For example, one resourceelement group may consist of four resource elements.

A plurality of PDCCHs may be transmitted in the control region. ThePDCCH carries control information such as scheduling allocation. ThePDCCH is transmitted on an aggregation of one or several consecutiveCCEs. A PDCCH format and the number of available PDCCH bits aredetermined according to the number of CCEs constituting the CCEaggregation. Hereinafter, the number of CCEs used for PDCCH transmissionis referred to as a CCE aggregation level. The CCE aggregation level isa CCE unit for searching for the PDCCH. A size of the CCE aggregationlevel is defined by the number of contiguous CCEs. For example, the CCEaggregation level may be an element off {1, 2, 4, 8}.

Table 1 below shows examples of the PDCCH format and the number ofavailable PDCCH bits according to the CCE aggregation level.

TABLE 1 PDCCH CCE aggregation Number of resource Number of PDCCH formatlevel element groups bits 0 1 9 72 1 2 18 144 2 4 36 288 3 8 72 576

Control information transmitted through the PDCCH is referred to asdownlink control information (hereinafter, DCI). The DCI transmitsuplink scheduling information, downlink scheduling information, systeminformation, uplink power control command, control information forpaging, control information indicating random access channel (RACH)response, etc. Further, the DCI may transmit control informationindicating activation of semi-persistent scheduling (SPS). The DCI mayalso transmit control information indicating deactivation of SPS. TheSPS may be used for uplink or downlink voice over Internet protocol(VoIP) transmission.

Examples of a DCI format include a format 0 for scheduling of a physicaluplink shared channel (PUSCH), a format 1 for scheduling of one physicaldownlink shared channel (PDSCH) codeword, a format 1A for compactscheduling of the one PDSCH codeword, a format 1B for scheduling ofsingle codeword rank-1 transmission in a spatial multiplexing mode, aformat 1C for very compact scheduling of a downlink shared channel(DL-SCH), a format 1D for scheduling of a PDSCH in a multi-user spatialmultiplexing mode, a format 2 for scheduling of the PDSCH in aclosed-loop spatial multiplexing mode, a format 2A for scheduling of thePDSCH in an open-loop spatial multiplexing mode, and formats 3 and 3Afor transmission of a transmission power control (TPC) command for anuplink channel.

FIG. 11 is a flowchart showing a PDCCH configuration.

Referring to FIG. 11, a BS generates control information according to aDCI format. The BS can select one DCI format from a plurality of DCIformats (DCI format 1, 2, . . . , N) according to the controlinformation to be transmitted to a UE.

In step S110, a cyclic redundancy check (CRC) is attached to detect anerror from control information generated according to each DCI format. Aunique identifier (i.e., a radio network temporary identifier (RNTI)) ismasked on the CRC according to a usage or an owner of the PDCCH. If thePDCCH is for a specific UE, a unique identifier of the UE (e.g.,cell-RNTI (C-RNTI)) can be masked on the CRC. That is, the CRC can bescrambled together with the unique identifier of the UE. Examples of theRNTI for the specific UE include a temporary C-RNTI, a semi-persistentC-RNTI, etc. The temporary C-RNTI is a temporary identifier of the UEand can be used during a random access procedure. The semi-persistentC-RNTI can be used to indicate SPS activation.

If the PDCCH is for a paging message transmitted through a PCH, a pagingidentifier (e.g., paging-RNTI (P-RNTI)) can be masked on the CRC. If thePDCCH is for system information transmitted through the DL-SCH, a systeminformation identifier (e.g., system information-RNTI (SI-RNTI)) can bemasked on the CRC. If the PDCCH is for indicating a random accessresponse that is a response for transmission of a random access preambleof the UE, a random access-RNTI (RA-RNTI) can be masked on the CRC.Table 2 below shows examples of identifiers masked on the PDCCH.

TABLE 2 Type Identifier Description UE- C-RNTI, temporary C- used for aunique specific RNTI, semi-persistent UE identification C-RNTI CommonP-RNTI used for paging message SI-RNTI used for system informationRA-RNTI used for random access response

When using a C-RNTI, a temporary C-RNTI, or a semi-persistent C-RNTI,the PDCCH carries control information for a corresponding specific UE.When using other RNTIs, the PDCCH carries common control information tobe received by all UEs in a cell.

In step S120, channel coding is performed on the CRC-attached controlinformation to generate coded data. In step S130, rate matching isperformed according to a CCE aggregation level assigned to the PDCCHformat.

In step S140, the coded data is modulated to generate modulationsymbols. The modulation symbols constituting one PDCCH may have one ofCCE aggregation levels 1, 2, 4, and 8. In step S150, the modulationsymbols are mapped to physical resource elements (REs) (i.e., CCE to REmapping).

FIG. 12 is a flowchart showing PDCCH processing.

Referring to FIG. 12, in step S210, a UE demaps a CCE from physical RE(i.e., CCE to RE demapping). In step S220, the UE demodulates respectiveCCE aggregation levels since the UE does not know which CCE aggregationlevel is used to receive the PDCCH. In step S230, the UE performs ratedematching to the demodulated data. Since the UE does not know a DCIformat of control information to be received by the UE, the UE performsthe rate dematching for the respective DCI formats. In step S240, the UEperforms channel decoding to the rate-dematched data according to a coderate, and detects an error by performing CRC checking. If no error isdetected, it is regarded that the UE detects its own PDCCH. Otherwise,if the error is detected, the UE continuously performs blind decoding onanother CCE aggregation level or another DCI format. In step S250, upondetecting its own PDCCH, the UE removes the CRC from the decoded dataand thus obtains the control information for the UE.

A plurality of multiplexed PDCCHs for a plurality of UEs can betransmitted within a control region of one subframe. The UE monitors thePDCCHs. The monitoring is an operation in which the UE attempts todecode respective PDCCHs according to monitored DCI formats. The BS doesnot provide information indicating a location of a corresponding PDCCHto the UE in the control region assigned within the subframe. The UEfinds its own PDCCH by monitoring a set of PDCCH candidates within thesubframe. This is called blind decoding (or blind detection). Throughthe blind decoding, the UE simultaneously performs identification of aPDCCH transmitted to the UE and performs decoding of the controlinformation transmitted through the PDCCH. For example, it is regardedthat the UE detects its own PDCCH if a CRC error is not detected bydemasking its own C-RNTI from the PDCCH.

The number of DCI formats to be transmitted through the PDCCH is limitedto effectively reduce an overhead of the blind decoding. The number ofDCI formats is less than the number of different types of controlinformation to be transmitted using the PDCCH. The DCI format includes aplurality of different information fields. A type of information fieldconstituting the DCI format, the number of information fields, thenumber of bits of each information field, and the like are differentaccording to the DCI format. In addition, a size of control informationconforming to the DCI format differs according to the DCI format. Avariety of control information is transmitted through the PDCCH by usingone of the limited number of DCI formats. That is, an arbitrary DCIformat can be used to transmit two or more pieces of control informationwith different types. Accordingly, when the control information isspecified by assigning specific values to a plurality of informationfields constituting a DCI format, some of the plurality of informationfields may be unnecessary. That is, specific values may not be definedin some of the plurality of information fields constituting the DCIformat. Some information fields constituting the DCI format may bereserved fields and thus may be reserved in a state of having arbitraryvalues. The information fields are reserved for the purpose of sizeadaptation so that a plurality of different types of control informationcan conform to one DCI format. However, if the reserved fields existwhen the control information is transmitted, the BS ineffectivelyconsumes transmission energy and transmission power to transmit thereserved fields which are not used in any functions. Therefore, when thecontrol information is generated conforming to the DCI format, there isa need for a method capable of utilizing unused information fields amongthe plurality of information fields constituting the DCI format.

FIG. 13 shows an example of a method for utilizing an unused informationfield among a plurality of information fields constituting a DCI format.

Referring to FIG. 13, different types of control information A, B, and Care grouped to use one DCI format. The control information A, B, and Cconforms to one DCI format. The DCI format consists of a plurality ofdifferent information fields. The control information A is specified byassigning specific values to all information fields of the DCI format.The control information B or C is specified by assigning specific valueto some information fields of the DCI format. The control information Ahas a greatest information bit size in the group. This is because allinformation fields of the DCI format are configured to be usedmeaningfully in the control information A. The information bit size ofthe control information A is a reference information bit size. Nullinformation is appended to the control information B or C to fit thesame size as the reference information bit size. Accordingly, thecontrol information A, B, and C in the group is fixed to the sameinformation bit size.

As such, the different types of control information are grouped toconform to one DCI format which is arbitrarily determined. Each piece ofcontrol information is specified by mapping a specific value to aninformation field constituting the DCI format. Arbitrary pieces ofcontrol information included in the group can be specified by assigningspecific values to all information fields of the DCI format. On theother hand, other control information included in the group can bespecified by assigning specific values to some information fields of theDCI format. That is, other information fields of the DCI format are notnecessary when the other control information is specified. A total sizeof information fields used to specify the control information can bedefined as an information bit size. An information bit size of theformer control information is the largest. An information bit size ofthe latter control information is relatively small.

The reference information bit size is defined as an information bit sizewhen control information is specified by assigning specific values toall information fields of the DCI format. The reference information bitsize denotes a total size of information fields constituting the DCIformat and/or a size of the DCI format itself. In a case where othercontrol information included in the group has an information bit sizeless than the reference information bit size, the null information isappended to fit the same size as the reference information bit size.That is, when specific control information is specified by assigningvalues to some information fields among all information fields definedin the DCI format, remaining information fields in which values are notassigned are used as the null information. The information fields usedas the null information can be referred to as an error check field.

The null information is appended so that control information conformingto the DCI format has the same size as the reference information bitsize of that DCI format. When the control information is generatedaccording to the DCI format, a part of unused information fields can beused as the null information. The null information has a specific value.For example, all bits of the information field used as the nullinformation may be all set to either bits of ‘0’ or bits of ‘1’.Alternatively, the field used as the null information may be set tobinary code stream values known to the UE. Such a binary code stream canbe named as a binary scramble code stream. The binary stream may begenerated according to a method for generating a binary bit stream knownto both the BS and the UE and for generating a Gold sequence or anm-sequence generated by the BS and the UE by using the same inputparameter.

The information field used as the null information may be predeterminedbetween the BS and the UE or may be reported by the BS to the UE. Forexample, the BS may report information regarding the information filedused as the null information to the UE by using RRC signaling or systeminformation.

When the UE monitors PDCCHs by performing CRC error detection, the UEmay erroneously recognize another UE's PDCCH as its own PDCCH, or whendemasking is performed with an RNTI different from an actual RNTI, theUE may erroneously recognize that no CRC error is detected and thusdecoding is successful. This is called a false positive error. To reducethe false positive error, the null information can be utilized as avirtual CRC or a probe for additional error check.

FIG. 14 is a flowchart showing a method for detecting controlinformation according to an embodiment of the present invention.

Referring to FIG. 14, a UE checks a CRC error by monitoring controlchannels (step S310). The control channels may be PDCCHs. If the CRCerror is detected, the UE continuously monitors the control channels(step S320). If no CRC error is detected, the UE determines whether avalue of an error check field is equal to a specific value (step S330).The error check field is one of fields included in control informationon a control channel in which the CRC error is not detected. The errorcheck field is information field used as null information among aplurality of information fields constituting the control information.

If the value of the error check field is not equal to the specificvalue, the UE continuously monitors the control channels (step S340).Otherwise, if the value of the error check field is equal to thespecific value, the UE detects the control information on the controlchannel, in which no CRC error is detected, as its own controlinformation (step S350). That is, only when the null information isdecoded to a specific value known to the UE, the control informationtransmitted through a corresponding PDCCH is received as the controlinformation of the UE.

Hereinafter, a method for transmitting control information using nullinformation will be described in detail. It is assumed that controlinformation is transmitted to indicate semi-persistent scheduling (SPS)activation by using a DCI format of a PDCCH defined for other usages.That is, the control information indicating SPS activation and othertypes of control information use one DCI format. SPS can be used foruplink or downlink VoIP transmission.

A radio resource scheduling scheme includes a dynamic scheduling scheme,a persistent scheduling scheme, and an SPS scheme. The dynamicscheduling scheme is a scheme in which scheduling information isrequested by using a control signal whenever data is transmitted orreceived. The persistent scheduling scheme is a scheme in whichpredetermined information is used so that scheduling information is notrequested by using the control signal whenever data is transmitted orreceived. The SPS scheme is a scheme in which scheduling information isnot requested during an SPS interval by using the control signalwhenever data is transmitted or received. The SPS interval can startupon receiving the control information indicating SPS activation. TheSPS interval can end upon receiving control information indicating SPSde-activation. Alternatively, the SPS interval can be determined throughRRC signaling.

FIG. 15 is a flow diagram showing downlink data transmission using thedynamic scheduling scheme. A BS transmits a downlink (DL) grant to a UEthrough a PDCCH whenever downlink data is transmitted through a PDSCH.The UE receives the downlink data transmitted through the PDSCH by usingthe DL grant received through the PDCCH. Advantageously, the BS canproperly schedule radio resources according to a downlink channelcondition.

FIG. 16 is a flow diagram showing uplink data transmission using thedynamic scheduling scheme. A BS allocates radio resources to a UEaccording to an uplink (UL) grant before uplink data is transmittedthrough a PUSCH. The UL grant is transmitted through a PDCCH.

A Voice over IP (VoIP) service provides voice data over an Internetprotocol (IP) network. Conventionally, the voice data has been providedin a circuit switched (CS) domain. In the VoIP service, however, thevoice data is provided in a packet switched (PS) domain. In CS-basedvoice services, the voice data is transmitted while maintaining aconnection in an end-to-end manner. On the other hand, in the VoIPservice, since the voice data can be transmitted in a connection-lessmanner, a network resource can be very effectively used.

With the development of a wireless communication technique, an amount ofuser data is rapidly increased. Thus, for effective use of a limitednetwork resource, the conventional CS-based services have recently beenreplaced with PS-based services. The VoIP service is being developed inthe same vein, and it is expected that all voice services are providedover the VoIP in most of wireless communication systems in the future.

A real-time transport protocol (RTP) is developed to effectively providethe PS-based voice services. Further, an RTP control protocol (RTCP) isalso developed to control the RTP. In the RTP, time stamp information iscarried in every packet, and thus a jitter problem can be solved.Further, an RTP packet loss is reported through the RTCP, and thus aframe error rate (FER) can be reduced through rate control. In additionto the RTP/RTCP, with the development of a session initiation protocol(SIP) and a session description protocol (SDP), a virtual connection canbe maintained in an end-to-end manner. Therefore, the delay problem canbe mostly solved.

FIG. 17 shows an example of a traffic model in a VoIP.

Referring to FIG. 17, two types of voice packets are generated in theVoIP, that is, a packet generated in a talk spurt and a packet generatedin a silence period. For example, if an adaptive multi-rate (AMR) of12.2 kbps is assumed, an RTP packet is generated in the talk spurt witha period of 20 ms, and has a size of 35 to 49 bytes. In the silenceperiod, the RTP packet is generated with a period of 160 ms, and has asize of 10 to 24 bytes.

When a packet is generated with a constant period in a voice servicesuch as a VoIP service, a size of the generated packet is relativelysmall and constant. Therefore, the VoIP generally uses the persistentscheduling scheme or the SPS scheme. When using the persistentscheduling scheme, radio resources are persistently allocated bypredicting the scheduling scheme in a radio bearer configurationprocess, and thus packets can be transmitted and received in the absenceof a control signal including scheduling information. When data istransmitted or received using the persistent scheduling scheme, achannel condition is not considered at a time point when the data istransmitted or received since a predetermined radio resource is usedwithout providing scheduling information. As a result, a transfer errorrate may be increased along with changes in the channel condition. TheVoIP is suitable to use the SPS scheme when the talk spurt is used as anSPS interval.

FIG. 18 is a flow diagram showing downlink data transmission using theSPS scheme. A BS transmits control information indicating SPS activationof resource allocation information to a UE through a PDCCH. During anSPS interval, the UE can receive VoIP data from the BS through a PDSCHby using the resource allocation information.

FIG. 19 is a flow diagram showing uplink data transmission using the SPSscheme. A BS transmits control information indicating SPS activation ofresource allocation information to a UE through a PDCCH. During an SPSinterval, the UE can transmit VoIP data to the BS through a PUSCH byusing the resource allocation information.

First, a method for transmitting control information indicating SPSactivation by using the DCI format 0 will be described. Controlinformation indicating PUSCH scheduling and the control informationindicating SPS activation can be transmitted by using the DCI format 0.The SPS activation can be used for uplink VoIP transmission.

Table 3 below shows examples of control information transmitted usingthe DCI format 0.

TABLE 3 Information Field bit(s) (1) Flag for format0/format1A 1differentiation (2) Hopping flag 1 (3) Resource block assignment andhopping ┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL) + 1)/2┐ resource allocation (4)Modulation and coding scheme and 5 redundancy version (5) New dataindicator 1 (6) TPC command for scheduled PUSCH 2 (7) Cyclic shift forDM RS 3 (8) UL index (TDD) 2 (9) CQI request i

The DCI format 0 includes a plurality of information fields. Theinformation fields are (1) a flag field, (2) a hopping flag field, (3) aresource block assignment and hopping resource allocation field, (4) amodulation and coding scheme (MCS) and redundancy version field, (5) anew data indicator field, (6) a TPC command field, (7) a cyclic shiftfield, (8) a UL index field, and (9) a channel quality indicator (CQI)request field. A bit size of each information field is for exemplarypurposes only, and thus the bit size is not limited thereto.

The flag field is an information field for differentiating the format 0from the format 1A. The resource block assignment and hopping resourceallocation field may have a bit size that varies according to a hoppingPUSCH or a non-hopping PUSCH. The resource block assignment and hoppingresource allocation field for the non-hopping PUSCH provides┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL)+1)/2)┐bits to allocate resources of a first slot in an uplink subframe.Herein,N_(RB) ^(UL)denotes the number of resource blocks included in an uplink slot, anddepends on an uplink Tx bandwidth determined in a cell. The resourceblock assignment and hopping resource allocation field for the hoppingPUSCH provides┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL)+1)/2)┐−N_(UL) _(_) _(hop)bits to allocate resources of the first slot in the uplink subframe.

If the number of information bits of the format 0 is less than thenumber of information bits of the format 1A, ‘0’ is appended to theformat 0 until a payload size becomes equal to a payload size of theformat 1A.

The control information for PUSCH scheduling is expressed using all ofthe afore-mentioned fields. Accordingly, control information having areference information bit size conforms to the DCT format 0 for PUSCHscheduling.

If the control information for SPS activation is transmitted using theDCI format 0, the null information appended to fit the referenceinformation bit size of the DCI format 0 can be used for virtual CRCcheck together with bits of ‘0’ padded to conform to the payload size ofthe format 1A.

Hereinafter, examples of the information field that can be used as thenull information when the control information for SPS activation istransmitted using the DCI format 0 will be described.

(1) 1st Embodiment

If it is assumed that a UE performs only PUCCH-based feedback withoutperforming aperiodic PUSCH feedback for downlink VoIP transmission, theCQI request field can be used as the null information.

Table 4 below shows the 1st embodiment of the control informationtransmitted using the DCI format 0 for PUSCH scheduling and SPSactivation.

TABLE 4 Information Field bit(s) . . . . . . . . . (9) CQI request 1 Forthe activation of uplink semi-persistent scheduling, this informationbit is set to zero.

If the control information is for uplink SPS activation, a value of theCQI request field is set to ‘0’. Remaining fields of the DCI format 0other than the CQI request field are the same as shown in Table 3 above.It is assumed that the UE performs only PUCCH-based feedback withoutperforming aperiodic PUSCH feedback for downlink VoIP transmission.

(2) 2nd Embodiment

It is assumed that control information indicating SPS activation foruplink VoIP packet transmission does not require additional closed-looppower control, and determines Tx power of VoIP transmission on the basisof open-loop type or hybrid type power control. When the TPC commandfield for a scheduled PUSCH is not used by considering assignment of asemi-static resource block, the TPC command field can be used as thenull information.

Table 5 below shows the 2nd embodiment of the control informationtransmitted using the DCI format 0 for PUSCH scheduling and SPSactivation.

TABLE 5 Information Field bit(s) . . . . . . . . . (6) TPC command forscheduled PUSCH 2 For the activation of uplink semi- persistentscheduling, this information bits is set to all zero. . . . . . . . . .

If the control information is for uplink SPS activation, values of theTPC command field are all set to ‘0’. Remaining fields of the DCI format0 other than the TPC command field are the same as shown in Table 3above.

(3) 3rd Embodiment

The control information indicating SPS activation for uplink VoIP packettransmission may not implicitly use the new data indicator field forspecific information delivery. In this case, the new data indicatorfield can be used as the null information.

Table 6 below shows the 3rd embodiment of the control informationtransmitted using the DCI format 0 for PUSCH scheduling and SPSactivation.

TABLE 6 Information Field bit(s) . . . . . . . . . (5) New dataindicator 1 For the activation of uplink semi- persistent scheduling,this information bit is set to zero. . . . . . . . . .

If the control information is for uplink SPS activation, a value of thenew data indicator field is set to ‘0’. Remaining fields of the DCIformat 0 other than the new data indicator field are the same as shownin Table 3 above.

(4) 4th Embodiment

The control information indicating SPS activation for uplink VoIP packettransmission can use additional signaling without indicating an MCS orredundancy version in the MCS and redundancy version field. When theadditional signaling is used without indicating the MCS in the MCS andredundancy version field, 3 bits out of 5 bits of the MCS and redundancyversion field can be used for the null information. When the additionalsignaling is used without indicating the redundancy version in theredundancy version filed, 2 bits out of the 5 bits can be used for thenull information. When the additional signaling is used both for the MCSand the redundancy version, the 5 bits can be all used for the nullinformation.

Table 7 below shows the 4th embodiment of the control informationtransmitted using the DCI format 0 for PUSCH scheduling and SPSactivation.

TABLE 7 Information Field bit(s) . . . . . . . . . (4) Modulation andcoding scheme and 5 redundancy version For the activation of uplinksemi- persistent scheduling, N information bits among 5 bits is set toall zero(N = 2, 3 or 5) . . . . . . . . . .

If the control information is for uplink SPS activation, 2, 3, or 5 bitsout of the 5 bits of the MCS and redundancy version field are set to‘0’. Remaining fields of the DCI format 0 other than the MCS andredundancy version field are the same as shown in Table 3 above.

(5) 5th Embodiment

The control information indicating SPS activation for uplink VoIP packettransmission may not additionally indicate the cyclic shift field for ademodulation reference symbol (DM-RS). In this case, the cyclic shiftfield is used for the null information.

Table 8 below shows the 5th embodiment of the control informationtransmitted using the DCI format 0 for PUSCH scheduling and SPSactivation.

TABLE 8 Information Field bit(s) . . . . . . . . . (7) Cyclic shift forDM RS 3 For the activation of uplink semi- persistent scheduling, thisinformation bits is set to all zero. . . . . . . . . .

If the control information is for uplink SPS activation, values of thecyclic shift field are all set to ‘0’. Remaining fields of the DCIformat 0 other than the TPC command field are the same as shown in Table3 above.

(6) 6th Embodiment

The control information indicating SPS activation for uplink VoIP packettransmission may allow the VoIP to limit a bandwidth that can beallocated over the entire system bandwidth. In this case, the resourceblock assignment and hopping resource allocation field can be used asthe null information. Among the┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL)+1)/2)┐

bits, M bits can be used for the null information. Herein, M is anatural number in the range of 1 to┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL)+1)/2)┐−1.

Table 9 below shows the 5th embodiment of the control informationtransmitted using the DCI format 0 for PUSCH scheduling and SPSactivation.

TABLE 9 Information Field bit(s) . . . . . . . . . (3) Resource blockassignment and hopping resource ┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL) + 1)/2)┐allocation For the activation of uplink semi-persistent scheduling Minformation bits among ┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL) + 1)/2)┐ bits isset to all zero. . . . . . . . . .

If the control information is for uplink SPS activation, the M bits outof the┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL)+1)/2)┐

bits are set to ‘0’. Herein, M is a natural number in the range of 1 to┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL)+1)/2)┐−1.

Remaining fields of the DCI format 0 other than the resource blockassignment and hopping resource allocation field are the same as shownin Table 3 above.

(7) 7th Embodiment

A combination of a plurality of information fields of the DCI format 0is used as the null information. Arbitrary information fields can becombined to be used as the null information. The entire informationfields can be used as the null information. The information fields usedas the null information in the 1st to 6th embodiments can be used in thecombination of the plurality of information fields. For example, whenthe additional signaling is used for the MCS or the redundancy versionas described in the 4th embodiment, the 2, 3, or 5 bits out of the 5bits of the MCS and redundancy version field can be used in acombination of the plurality of information fields. When using afrequency division duplex (FDD) system, bits of the uplink index fieldcan be used as the null information by appending them to the informationfields used as the null information in the 1st to 6th embodiments.

(8) 8th Embodiment

The 8th embodiment is a detailed embodiment of the 7th embodiment. Ifthe control information for SPS activation is transmitted using the DCTformat 0, a combination of the resource block assignment and hoppingresource allocation field, the MCS and redundancy version field, the TPCcommand field, the cyclic shift field, and the CQI request field can beused as the null information.

Table 10 below shows the 8th embodiment of the control informationtransmitted using the DCI format 0 for PUSCH scheduling and SPSactivation.

TABLE 10 Information Field bit(s) . . . . . . . . . (3) Resource blockassignment and hopping resource ┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL) + 1)/2)┐allocation For the activation of uplink semi-persistent scheduling M(M =1, 2, . . . , ┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL) + 1)/2)┐ − 1) informationbits among ┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL) + 1)/2)┐ bits is set to allzero. (4) Modulation and coding scheme and redundancy 5 version For theactivation of uplink semi-persistent scheduling, N information bitsamong 5 bits is set to all zero. (5) New data indicator 1 (6) TPCcommand for scheduled PUSCH 2 For the activation of uplinksemi-persistent scheduling, this information bits is set to all zero.(7) Cyclic shift for DM RS 3 For the activation of uplinksemi-persistent scheduling, this information bits is set to all zero.(8) UL index (TDD) 2 (9) CQI request 1 For the activation of uplinksemi-persistent scheduling, this information bit is set to zero.

Herein, M of the resource block assignment and hopping resourceallocation may be specifically set to ‘2’, and N of the MCS andredundancy version field may be specifically set to ‘1’.

(9) 9th Embodiment

The 9th embodiment is a detailed embodiment of the 7th embodiment. Ifthe control information for SPS activation is transmitted using the DCIformat 0, a combination of the resource block assignment and hoppingresource allocation field, the MCS and redundancy version field, the newdata indicator field, the TPC command field, the cyclic shift field, andthe CQI request field can be used as the null information. This is acase where the new data indicator field is added to the combination ofthe information fields of the 8th embodiment so as to be used as thenull information.

Table 11 below shows the 9th embodiment of the control informationtransmitted using the DCI format 0 for PUSCH scheduling and SPSactivation.

TABLE 11 Information Field bit(s) . . . . . . . . . (3) Resource blockassignment and hopping resource ┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL) + 1)/2)┐allocation For the activation of uplink semi-persistent scheduling M(M =1, 2, . . . , ┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL) + 1)/2)┐ − 1) informationbits among ┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL) + 1)/2)┐ bits is set to allzero. (4) Modulation and coding scheme and redundancy 5 version For theactivation of uplink semi-persistent scheduling, N information bitsamong 5 bits is set to all zero. (5) New data indicator 1 For theactivation of uplink semi-persistent scheduling, this information bit isset to all zero. (6) TPC command for scheduled PUSCH 2 For theactivation of uplink semi-persistent scheduling, this information bitsis set to all zero. (7) Cyclic shift for DM RS 3 For the activation ofuplink semi-persistent scheduling, this information bits is set to allzero. (8) UL index (TDD) 2 (9) CQI request 1 For the activation ofuplink semi-persistent scheduling, this information bit is set to zero.

Herein, M of the resource block assignment and hopping resourceallocation may be specifically set to ‘2’, and N of the MCS andredundancy version field may be specifically set to ‘1’.

(10) 10th Embodiment

The 10th embodiment is a detailed embodiment of the 7th embodiment. Ifthe control information for SPS activation is transmitted using the DCIformat 0, according to a relation between the resource block assignmentand hopping resource allocation field and the MCS and redundancy versionfield, the null information can be used for the two fields. The twofields can be related by additional indication of RRC. In addition tothe two fields, a combination of the TPC command field, the cyclic shiftfield, and the CQI request field can be used as the null information.

Table 12 below shows the 10th embodiment of the control informationtransmitted using the DCI format 0 for PUSCH scheduling and SPSactivation.

TABLE 12 Information Field bit(s) . . . . . . . . . (3) Resource blockassignment and hopping resource ┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL) + 1)/2)┐allocation (4) Modulation and coding scheme and redundancy 5 version Forthe activation of uplink semi-persistent scheduling, R information bitsfrom “Resource block assignment and hopping resource allocation andModulation and coding scheme and redundancy version” is set to all zero.(5) New data indicator 1 (6) TPC command for scheduled PUSCH 2 For theactivation of uplink semi-persistent scheduling, this information bitsis set to all zero. (7) Cyclic shift for DM RS 3 For the activation ofuplink semi-persistent scheduling, this information bits is set to allzero. (8) UL index (TDD) 2 (9) CQI request 1 For the activation ofuplink semi-persistent scheduling, this information bit is set to zero.

Herein, R may be 1, 2, . . . , or may be┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL)+1)/2)┐

+4 bits. Alternatively, R may be specifically set to ‘3’ or ‘4’.

(11) 11th Embodiment

The 11th embodiment is a detailed embodiment of the 7th embodiment. Ifthe control information for SPS activation is transmitted using the DCIformat 0, the new data indicator field is added to the combination ofthe information fields of the 10th embodiment so as to be used as thenull information.

Table 13 below shows the 11th embodiment of the control informationtransmitted using the DCI format 0 for PUSCH scheduling and SPSactivation.

TABLE 13 Information Field bit(s) . . . . . . . . . (3) Resource blockassignment and hopping resource ┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL) + 1)/2)┐allocation (4) Modulation and coding scheme and redundancy 5 version Forthe activation of uplink semi-persistent scheduling, R information bitsfrom “Resource block assignment and hopping resource allocation andModulation and coding scheme and redundancy version” is set to all zero.(5) New data indicator 1 For the activation of uplink semi-persistentscheduling, this information bit is set to all zero. (6) TPC command forscheduled PUSCH 2 For the activation of uplink semi-persistentscheduling, this information bits is set to all zero. (7) Cyclic shiftfor DM RS 3 For the activation of uplink semi-persistent scheduling,this information bits is set to all zero. (8) UL index (TDD) 2 (9) CQIrequest 1 For the activation of uplink semi-persistent scheduling, thisinformation bit is set to zero.

Herein, R may be 1, 2, . . . , or may be┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL)+1)/2)┐

+4 bits. Alternatively, R may be specifically set to ‘3’ or ‘4’.

Now, a method for transmitting the control information indicating SPSactivation by using the DCI format 1A will be described. The DCI format1A can be used to transmit control information for compact scheduling ofone PDSCH codeword and the control information indicating SPSactivation. The SPS activation can be used for uplink VoIP transmission.

Table 14 below shows examples of the control information transmittedusing the DCI format 1A.

TABLE 14 Information Field bit(s) (1) Flag for format0/format1A 1differentiation (2) Localized/Distributed VRB 1 assignment flag (3)Resource block assignment ┌log₂(N_(RB) ^(DL)(N_(RB) ^(DL) + 1)/2)┐ (4)Modulation and coding scheme 5 (5) HARQ process number 3 or 4 (6) Newdata indicator 1 (7) Redundancy version 2 (8) TPC command for scheduledPUCCH 2 (9) Downlink Assignment Index (TDD) 2

The DCI format 1A includes a plurality of information fields. Theinformation fields are (1) a flag field, (2) a localized/distributedvirtual resource block (VRB) assignment flag field, (3) a resource blockassignment field, (4) a modulation and coding scheme (MCS) field, (5) ahybrid automatic repeat request (HARQ) process number field, (6) a newdata indicator field, (7) a redundancy version field, (8) a TPC commandfield, and (9) a downlink assignment index field. A bit size of eachinformation field is for exemplary purposes only, and thus the bit sizeis not limited thereto.

The flag field is an information field for differentiating the format 0from the format 1A. If a CRC of the DCI format 1A is scrambled with anRA-RNTI, P-RNTI, or SI-RNTI, a bit of the flag field indicates a columnN_(PRB) ^(1A)

of a transport block size (TBS) table. If the flag field is ‘0’,N_(PRB) ^(1A)

is 20. If the flag field is ‘1’,N_(PRB) ^(1A)

is ‘3’. Otherwise, the flag field indicates the DCI format.

The resource block assignment field may have a bit size that variesaccording to a localized VRB or a distributed VRB. The resource blockassignment field for the localized VRB provides┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL)+1)/2)┐

bits for resource assignment. Herein,N_(RB) ^(DL)denotes the number of resource blocks included in a downlink slot, anddepends on a downlink Tx bandwidth determined in a cell. The resourceblock assignment field for the distributed VRB varies according towhetherN_(RB) ^(DL)is less than 50 or whetherN_(RB) ^(DL)is greater than or equal to 50.IfN_(RB) ^(DL)

is less than 50 or if the CRC of the DCI format 1A is scrambled with theRA-RNTI, P-RNTI, or SI-RNTI,┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL)+1)/2)┐

bits are provided for resource assignment. IfN_(RB) ^(DL)

is greater than or equal to 50,┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL)+1)/2)┐−1

bits are provided for resource assignment.

If the CRC of the DCT format 1A is scrambled with the RA-RNTT, P-RNTT,or ST-RNTI, the new data indicator field indicates a gap value. Forexample, if the new data indicator field is ‘0’, Ngap is Ngap,1. If thenew data indicator field is ‘1’, Ngap is Ngap,2. Otherwise, the new dataindicator field indicates new data.

Control information indicating channel assignment on the PDSCH can isexpressed using all of the aforementioned fields. Accordingly, controlinformation having a reference information size conforms to the DCIformat 1A used to assign channels for the PDSCH.

Hereinafter, examples of the information field that can be used as thenull information when the control information for SPS activation istransmitted using the DCI format 1A will be described.

(12) 12th Embodiment

Control information indicating SPS activation for downlink VoIP packettransmission does not have to report an HARQ process number for downlinkVoIP transmission. In this case, the HARQ process number field can beused as the null information. For example, if it is assumed that a UEperforms only PUCCH-based feedback without performing aperiodic PUSCHfeedback for downlink VoIP transmission, the HARQ process number fieldcan be used as the null information.

Table 15 below shows the 12th embodiment of the control informationtransmitted using the DCT format 1A for PDSCH channel assignment and SPSactivation.

TABLE 15 Information Field bit(s) . . . . . . . . . (5) HARQ processnumber 3 or 4 For the activation of downlink semi-persistent scheduling,this information bits is set to all zero. . . . . . . . . .

If the control information is for downlink SPS activation, the HARQprocess number field is set to ‘0’. Remaining fields of the DCI format1A other than the HARQ process number field are the same as shown inTable 14 above.

(13) 13th Embodiment

It is assumed that control information indicating SPS activation fordownlink VoIP packet transmission does not require additionalclosed-loop power control, and determines Tx power of PUCCH transmissionon the basis of open-loop type or hybrid type power control. When theTPC command field is not used by considering assignment of a semi-staticresource block, the TPC command field can be used as the nullinformation.

Table 16 below shows the 13th embodiment of the control informationtransmitted using the DCI format 1A for PDSCH channel assignment and SPSactivation.

TABLE 16 Information Field bit(s) . . . . . . . . . (8) TPC command forscheduled PUCCH 2 For the activation of downlink semi-persistentscheduling, this information bits is set to all zero. . . . . . . . . .

If the control information is for downlink SPS activation, values of theTPC command fields are all set to ‘0’. Remaining fields of the DCIformat 1A other than the TPC command field are the same as shown inTable 14 above.

(14) 14th Embodiment

The control information indicating SPS activation for downlink VoIPpacket may not implicitly use the new data indicator field for specificinformation delivery. In this case, the new data indicator field can beused as the null information.

Table 17 below shows the 14th embodiment of the control informationtransmitted using the DCI format 1A for PDSCH channel assignment and SPSactivation.

TABLE 17 Information Field bit(s) . . . . . . . . . (6) New dataindicator 1 For the activation of downlink semi-persistent scheduling,this information bit is set to zero. . . . . . . . . .

If the control information is for downlink SPS activation, a value ofthe new data indicator field is set to ‘0’. Remaining fields of the DCIformat 1A other than the new data indicator field are the same as shownin Table 14 above.

(15) 15th Embodiment

The control information indicating SPS activation for downlink VoIPpacket may not implicitly use the redundancy version field for specificinformation delivery. In this case, the redundancy version field can beused as the null information.

Table 18 below shows the 14th embodiment of the control informationtransmitted using the DCI format 1A for PDSCH channel assignment and SPSactivation.

TABLE 18 Information Field bit(s) . . . . . . . . . (7) Redundancyversion 2 For the activation of downlink semi-persistent scheduling,this information bits is set to all zero. . . . . . . . . .

If the control information is for downlink SPS activation, values of theredundancy version field are all set to ‘0’. Remaining fields of the DCIformat 1A other than the redundancy version field are the same as shownin Table 14 above.

(16) 16th Embodiment

The control information indicating SPS activation for downlink VoIPpacket can use additional signaling without indicating an MCS in the MCSfield. Alternatively, some of all possible cases of modulation schemesand coding rates may be used. In this case, Q bits out of the 5 bits ofthe MCS field can be used as the null information. Herein, Q is anatural number in the range of 1 to 5.

Table 19 below shows the 16th embodiment of the control informationtransmitted using the DCI format 1A for PDSCH channel assignment and SPSactivation.

TABLE 19 Information Field bit(s) . . . . . . . . . (4) Modulation andcoding scheme 5 For the activation of downlink semi-persistentscheduling, Q information bits among 5 bits is set to all zero. . . . .. . . . .

If the control information is for downlink SPS activation, the Q bitsout of the 5 bits of the MCS field are set to ‘0’. Herein, Q is anatural number in the range of 1 to 5. Remaining fields of the DCIformat 1A other than the MCS field are the same as shown in Table 14above.

(17) 17th Embodiment

The control information indicating SPS activation for downlink VoIPpacket may allow the VoIP to limit a bandwidth that can be allocatedover the entire system bandwidth. In this case, the resource blockassignment field can be used as the null information. Among┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL)+1)/2)┐

bits, P bits can be used for the null information. Herein, P is anatural number in the range of 1 to┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL)+1)/2)┐−1.

Table 20 below shows the 17th embodiment of the control informationtransmitted using the DCI format 1A for PDSCH channel assignment and SPSactivation.

TABLE 20 Information Field bit(s) . . . . . . . . . (3) Resource blockassignment ┌log₂(N_(RB) ^(DL)(N_(RB) ^(DL) + 1)/2)┐ For the activationof downlink semi-persistent scheduling P information bits among┌log₂(N_(RB) ^(DL)(N_(RB) ^(DL) + 1)/2)┐ bits is set to all zero. . . .. . . . . .

If the control information is for downlink SPS activation, the P bitsout of the┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL)+1)/2)┐

bits are set to ‘0’. Herein, P is a natural number in the range of 1 to┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL)+1)/2)┐−1.

Remaining fields of the DCI format 1A other than the resource blockassignment field are the same as shown in Table 14 above.

(18) 18th Embodiment

A combination of a plurality of information fields of the DCI format 1Ais used as the null information. Arbitrary information fields can becombined to be used as the null information. The entire informationfields can be used as the null information. The information fields usedas the null information in the 12th to 17th embodiments can be used inthe combination of the plurality of information fields. For example,when the additional signaling is used for the MCS as described in the16th embodiment, the Q bits out of the 5 bits of the MCS field can beused in a combination of the plurality of information fields. Herein, Qis a natural number in the range of 1 to 5. In addition, as in the 17thembodiment, the P bits out of the┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL)+1)/2)┐bits of the resource block assignment field can be used in a combinationof the information fields. Herein, P is a natural number in the range of1 to┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL)+1)/2)┐−1.When using the FDD system, bits of the downlink index field can be usedas the null information by appending them to the information fields usedas the null information in the 12th to 17th embodiments.

(19) 19th Embodiment

The 19th embodiment is a detailed embodiment of the 18th embodiment. Ifthe control information for SPS activation is transmitted using the DCIformat 1A, a combination of the resource block assignment field, the MCSfield, and the redundancy version field is used as the null information.

Table 21 below shows the 19th embodiment of the control informationtransmitted using the DCI format 1A for PDSCH channel assignment and SPSactivation.

TABLE 21 Information Field bit(s) (1) Flag for format0/format1Adifferentiation 1 (2) Localized/Distributed VRB assignment flag 1 (3)Resource block assignment ┌log₂(N_(RB) ^(DL)(N_(RB) ^(DL) + 1)/2)┐ Forthe activation of downlink semi-persistent scheduling P information bitsamong ┌log₂(N_(RB) ^(DL)(N_(RB) ^(DL) + 1)/2)┐ bits is set to all zero.(4) Modulation and coding scheme 5 For the activation of downlinksemi-persistent scheduling, Q information bits among 5 bits is set toall zero. (5) HARQ process number 3 or 4 (6) New data indicator 1 (7)Redundancy version 2 For the activation of downlink semi-persistentscheduling, this information bits is set to all zero. (8) TPC commandfor scheduled PUCCH 2 (9) Downlink Assignment Index (TDD) 2

(20) 20th Embodiment

The 20th embodiment is a detailed embodiment of the 18th embodiment. Ifthe control information for SPS activation is transmitted using the DCIformat 1A, a combination of the resource block assignment field, the MCSfield, the new data indicator field, and the redundancy version is usedas the null information. This is a case where the new data indicatorfield is added to the combination of the information fields of the 19thembodiment so as to be used as the null information.

Table 22 below shows the 20th embodiment of the control informationtransmitted using the DCI format 1A for PDSCH channel assignment and SPSactivation.

TABLE 22 Information Field bit(s) (1) Flag for format0/format1Adifferentiation 1 (2) Localized/Distributed VRB assignment flag 1 (3)Resource block assignment ┌log₂(N_(RB) ^(DL)(N_(RB) ^(DL) + 1)/2)┐ Forthe activation of downlink semi-persistent scheduling P information bitsamong ┌log₂(N_(RB) ^(DL)(N_(RB) ^(DL) + 1)/2)┐ bits is set to all zero.(4) Modulation and coding scheme 5 For the activation of downlinksemi-persistent scheduling, Q information bits among 5 bits is set toall zero. (5) HARQ process number 3 or 4 (6) New data indicator 1 Forthe activation of downlink semi-persistent scheduling, this informationbits is set to zero. (7) Redundancy version 2 For the activation ofdownlink semi-persistent scheduling, this information bits is set to allzero. (8) TPC command for scheduled PUCCH 2 (9) Downlink AssignmentIndex (TDD) 2

(21) 21st Embodiment

The 21st embodiment is a detailed embodiment of the 18th embodiment. Ifthe control information for SPS activation is transmitted using the DCIformat 1A, a combination of the resource block assignment field, the MCSfield, the HARQ process number field, and the redundancy version fieldis used as the null information. This is a case where the HARQ processnumber field is added to the combination of the information fields ofthe 19th embodiment so as to be used as the null information.

TABLE 23 Information Field bit(s) (1) Flag for format0/format1Adifferentiation 1 (2) Localized/Distributed VRB assignment flag 1 (3)Resource block assignment ┌log₂(N_(RB) ^(DL)(N_(RB) ^(DL) + 1)/2)┐ Forthe activation of downlink semi-persistent scheduling P information bitsamong ┌log₂(N_(RB) ^(DL)(N_(RB) ^(DL) + 1)/2)┐ bits is set to all zero.(4) Modulation and coding scheme 0 For the activation of downlinksemi-persistent scheduling, Q information bits among 5 bits is set toall zero. (5) HARQ process number 3 or 4 For the activation of downlinksemi-persistent scheduling, this information bits is set to all zero.(6) New data indicator 1 (7) Redundancy version 2 For the activation ofdownlink semi-persistent scheduling, this information bits is set to allzero. (8) TPC command for scheduled PUCCH 2 (9) Downlink AssignmentIndex (TDD) 2

(22) 22nd Embodiment

The 22nd embodiment is a detailed embodiment of the 18th embodiment. Ifthe control information for SPS activation is transmitted using the DCIformat 1A, a combination of the resource block assignment field, the MCSfield, the HARQ process number field, the new data indicator field, andthe redundancy version field is used as the null information. This is acase where the new data indicator field is added to the combination ofthe information fields of the 21st embodiment so as to be used as thenull information.

TABLE 24 Information Field bit(s) (1) Flag for format0/format1Adifferentiation 1 (2) Localized/Distributed VRB assignment flag 1 (3)Resource block assignment ┌log₂(N_(RB) ^(DL)(N_(RB) ^(DL) + 1)/2)┐ Forthe activation of downlink semi-persistent scheduling P information bitsamong ┌log₂(N_(RB) ^(DL)(N_(RB) ^(DL) + 1)/2)┐ bits is set to all zero.(4) Modulation and coding scheme 5 For the activation of downlinksemi-persistent scheduling, Q information bits among 5 bits is set toall zero. (5) HARQ process number 3 or 4 For the activation of downlinksemi-persistent scheduling, this information bits is set to all zero.(6) New data indicator 1 For the activation of downlink semi-persistentscheduling, this information bits is set to zero. (7) Redundancy version2 For the activation of downlink semi persistent scheduling, thisinformation bits is set to all zero. (8) TPC command for scheduled PUCCH2 (9) Downlink Assignment Index (TDD) 2

(23) 23rd Embodiment

The 23rd embodiment is a detailed embodiment of the 18th embodiment. Ifthe control information for SPS activation is transmitted using the DCIformat 1A, according to a relation between the resource block assignmentfield and the MCS field, the null information can be used for the twofields. The two fields can be related by additional indication of RRC.In addition to the two fields, the redundancy version field can befurther combined to be used as the null information.

Table 25 below shows the 23rd embodiment of the control informationtransmitted using the DCI format 1A for PDSCH channel assignment and SPSactivation.

TABLE 25 Information Field bit(s) (1) Flag for format0/format1Adifferentiation 1 (2) Localized/Distributed VRB assignment flag 1 (3)Resource block assignment ┌log₂(N_(RB) ^(DL)(N_(RB) ^(DL) + 1)/2)┐ (4)Modulation and coding scheme 5 For the activation of downlinksemi-persistent scheduling, S information bits from “Resource blockassignment” and “Modulation and coding scheme” is set to all zero. (5)HARQ process number 3 or 4 (6) New data indicator 1 (7) Redundancyversion 2 For the activation of downlink semi-persistent scheduling,this information bits is set to all zero. (8) TPC command for scheduledPUCCH 2 (9) Downlink Assignment Index (TDD) 2

Herein, S may be 1, 2, . . . , or may be┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL)+1)/2)┐

+4 bits.

(24) 24th Embodiment

The 24th embodiment is a detailed embodiment of the 18th embodiment. Ifthe control information for SPS activation is transmitted using the DCIformat 1A, according to a relation between the resource block assignmentfield and the MCS field, the null information can be used for the twofields. The two fields can be related by additional indication of RRC.In addition to the two fields, a combination of the new data indicatorfield and the redundancy version field can be used as the nullinformation. This is a case where the new data indicator field is addedto the combination of the information fields of the 23rd embodiment soas to be used as the null information.

Table 26 below shows the 24th embodiment of the control informationtransmitted using the DCI format 1A for PDSCH channel assignment and SPSactivation.

TABLE 26 Information Field bit(s) (1) Flag for format0/format1Adifferentiation 1 (2) Localized/Distributed VRB assignment flag 1 (3)Resource block assignment ┌log₂(N_(RB) ^(DL)(N_(RB) ^(DL) + 1)/2)┐ (4)Modulation and coding scheme 5 For the activation of downlinksemi-persistent scheduling, S information bits from “Resource blockassignment” and “Modulation and coding scheme” is set to all zero. (5)HARQ process number 3 or 4 (6) New data indicator 1 For the activationof downlink semi-persistent scheduling, this information bits is set tozero. (7) Redundancy version 2 For the activation of downlinksemi-persistent scheduling, this information bits is set to all zero.(8) TPC command for scheduled PUCCH 2 (9) Downlink Assignment Index(TDD) 2

Herein, S may be 1, 2, . . . , or may be┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL)+1)/2)┐

+4 bits.

(25) 25th Embodiment

The 25th embodiment is a detailed embodiment of the 18th embodiment. Ifthe control information for SPS activation is transmitted using the DCIformat 1A, according to a relation between the resource block assignmentfield and the MCS field, the null information can be used for the twofields. The two fields can be related by additional indication of RRC.In addition to the two fields, a combination of the HARQ process numberfield and the redundancy version field can be used as the nullinformation. This is a case where the HARQ process number field is addedto the combination of the information fields of the 23rd embodiment soas to be used as the null information.

Table 27 below shows the 25th embodiment of the control informationtransmitted using the DCI format 1A for PDSCH channel assignment and SPSactivation.

TABLE 27 Information Field bit(s) (1) Flag for format0/format1Adifferentiation 1 (2) Localized/Distributed VRB assignment flag 1 (3)Resource block assignment ┌log₂(N_(RB) ^(DL)(N_(RB) ^(DL) + 1)/2)┐ (4)Modulation and coding scheme 5 For the activation of downlinksemi-persistent scheduling, S information bits from “Resource blockassignment” and “Modulation and coding scheme” is set to all zero. (5)HARQ process number 3 or 4 For the activation of downlinksemi-persistent scheduling, this information bits is set to all zero.(6) New data indicator 1 (7) Redundancy version 2 For the activation ofdownlink semi-persistent scheduling, this information bits is set to allzero. (8) TPC command for scheduled PUCCH 2 (9) Downlink AssignmentIndex (TDD) 2

Herein, S may be 1, 2, . . . , or may be┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL)+1)/2)┐

+4 bits.

(26) 26th Embodiment

The 26th embodiment is a detailed embodiment of the 18th embodiment. Ifthe control information for SPS activation is transmitted using the DCIformat 1A, according to a relation between the resource block assignmentfield and the MCS field, the null information can be used for the twofields. The two fields can be related by additional indication of RRC.In addition to the two fields, a combination of the HARQ process numberfield, the new data indicator field, and the redundancy version fieldcan be used as the null information. This is a case where the new dataindicator field is added to the combination of the information fields ofthe 25th embodiment so as to be used as the null information.

Table 28 below shows the 26th embodiment of the control informationtransmitted using the DCI format 1A for PDSCH channel assignment and SPSactivation.

TABLE 28 Information Field bit(s) (1) Flag for format0/format1Adifferentiation 1 (2) Localized/Distributed VRB assignment flag 1 (3)Resource block assignment ┌log₂(N_(RB) ^(DL)(N_(RB) ^(DL) + 1)/2)┐ (4)Modulation and coding scheme 5 For the activation of downlinksemi-persistent scheduling, S information bits from “Resource blockassignment” and “Modulation and coding scheme” is set to all zero. (5)HARQ process number 3 or 4 For the activation of downlinksemi-persistent scheduling, this information bits is set to all zero.(6) New data indicator 1 For the activation of downlink semi-persistentscheduling, this information bits is set to zero. (7) Redundancy version2 For the activation of downlink semi-persistent scheduling, thisinformation bits is set to all zero. (8) TPC command for scheduled PUCCH2 (9) Downlink Assignment Index (TDD) 2

Herein, S may be 1, 2, . . . , or may be┌log₂(N_(RB) ^(UL)(N_(RB) ^(UL)+1)/2)┐

4 bits.

(27) 27th Embodiment

The DCI format 1 can be used to transmit control information for channelassignment on a PDSCH based on general resource allocation and controlinformation indicating SPS activation for downlink VoIP packettransmission. In a method of the 12th to 26th embodiments, theinformation fields defined in the DCI format 1A are used as the nullinformation in a condition where control information indicating channelassignment on a PDSCH based on specific resource allocation and controlinformation indicating SPS activation for downlink VoIP packettransmission are transmitted using the DCI format 1A. The method of the12th to 26th embodiments can be equally applied to a case where thecontrol information indicating SPS activation is transmitted using theDCI format 1. Information fields defined in the DCI format 1 may also beused as the null information.

(28) 28th Embodiment

The DCI format 2 can be used to transmit control information for PDSCHscheduling for a UE which is set to a spatial multiplexing mode andcontrol information for SPS activation for downlink VoIP packettransmission. The method of the 12th to 26th embodiments can be equallyapplied to a case where the control information for SPS activation istransmitted using the DCI format 2. Information fields defined in theDCI format 2 may also be used as the null information.

The DCI format 2 includes a HARQ swap flag field. The HARQ swap flagfield can also be used as the null information by being appended to theinformation fields used as the null information in the DCI format 2. Allpossible combinations of the HARQ swap flag field and other informationfields can also be used as the null information.

As described above, a method for detecting control information canprovided with an increased accuracy in a wireless communication system.A specific value of an error check field can be used as a virtual CRC. Auser equipment can increase an accuracy of CRC error checking by usingthe virtual CRC when detecting the control information. That is, thecontrol information can be accurately detected while effectivelyutilizing radio resources. Therefore, an overall system performance canbe increased.

All functions described above may be performed by a processor such as amicro-processor, a controller, a microcontroller, and an applicationspecific integrated circuit (ASIC) according to software or program codefor performing the functions. The program code may be designed,developed, and implemented on the basis of the descriptions of thepresent invention, and this is well known to those skilled in the art.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those skilled in the art that various changes in form and details maybe made therein without departing from the spirit and scope of theinvention as defined by the appended claims. The exemplary embodimentsshould be considered in descriptive sense only and not for purposes oflimitation. Therefore, the scope of the invention is defined not by thedetailed description of the invention but by the appended claims, andall differences within the scope will be construed as being included inthe present invention.

The invention claimed is:
 1. A method for detecting control information in a wireless communication system using a downlink slot comprising a plurality of orthogonal frequency-division multiplexing (OFDM) symbols, the method comprising: monitoring a physical downlink control channel (PDCCH), and de-masking cyclic redundancy check (CRC) bits included in the PDCCH by using a user equipment identifier (UE-ID); checking a cyclic redundancy check (CRC) error of the de-masked CRC bits; and if the CRC error is not detected, determining whether to activate semi-persistent scheduling (SPS) based on a new data indicator (NDI) and control bits for a cyclic shift for DeModulation Reference Signal (DM RS), wherein the NDI is an 1-bit information field included in downlink control information (DCI) on the PDCCH, wherein the control bits for the cyclic shift for the DM RS are included in the DCI on the PDCCH, wherein the SPS is activated if the NDI is equal to zero and at least one predefined bit of the control bits for the cyclic shift for the DM RS is equal to zero.
 2. The method of claim 1, wherein the cyclic shift for the DM RS is a 3-bit information field.
 3. The method of claim 2, wherein the SPS is activated if the NDI is equal to zero and the control bits for the cyclic shift for the DM RS is set to ‘000’.
 4. The method of claim 1, wherein the DCI is DCI format 0, which is used for scheduling of the PUSCH.
 5. The method of claim 1, wherein the UE-ID is a semi-persistent cell-radio network temporary identifier (C-RNTI).
 6. A user equipment in a wireless communication system using a downlink slot comprising a plurality of orthogonal frequency-division multiplexing (OFDM) symbols, comprising: a radio frequency (RF) unit for transmitting and receiving a radio signal; and a processor coupled with the RF unit and configured to: monitor a physical downlink control channel (PDCCH), de-mask cyclic redundancy check (CRC) bits included in the PDCCH by using a user equipment identifier (UE-ID); check a cyclic redundancy check (CRC) error of the de-masked CRC bits; if the CRC error is not detected, determining whether to activate semi-persistent scheduling (SPS) based on a new data indicator (NDI) and control bits for a cyclic shift for DeModulation Reference Signal (DM RS), wherein the NDI is an 1-bit information field included in downlink control information (DCI) on the PDCCH, wherein the control bits for the cyclic shift for the DM RS are included in the DCI on the PDCCH, wherein the SPS is activated if the NDI is equal to zero and at least one predefined bit of the control bits for the cyclic shift for the DM RS is equal to zero.
 7. The user equipment of claim 6, wherein the cyclic shift for the DM RS is a 3-bit information field.
 8. The user equipment of claim 7, wherein the SPS is activated if the NDI is equal to zero and the control bits for the cyclic shift for the DM RS is set to ‘000’.
 9. The user equipment of claim 6, wherein the DCI is DCI format 0, which is used for scheduling of the PUSCH.
 10. The user equipment of claim 6, wherein the UE-ID is a semi-persistent cell-radio network temporary identifier (C-RNTI).
 11. A user equipment in a wireless communication system using a downlink slot comprising a plurality of orthogonal frequency-division multiplexing (OFDM) symbols, comprising: a radio frequency (RF) unit for transmitting and receiving a radio signal; and a processor coupled with the RF unit and configured to: monitor a physical downlink control channel (PDCCH), de-mask cyclic redundancy check (CRC) bits included in the PDCCH by using a user equipment identifier (UE-ID); check a cyclic redundancy check (CRC) error of the de-masked CRC bits; if the CRC error is not detected, and downlink control information (DCI) on the PDCCH is DCI format 0 used for scheduling of a Physical Uplink Shared Channel (PUSCH), determine whether to activate semi-persistent scheduling (SPS) based on a new data indicator (NDI) and control bits for a cyclic shift for DeModulation Reference Signal (DM RS), wherein the NDI is an 1-bit information field included in the DCI, wherein the control bits for the cyclic shift for DM RS are included in the DCI, wherein the SPS is activated if the NDI is equal to zero and at least one predefined bit of the control bits for the cyclic shift for the DM RS is equal to zero.
 12. The user equipment of claim 11, wherein the cyclic shift for the DM RS is a 3-bit information field.
 13. The user equipment of claim 12, wherein the SPS is activated if the NDI is equal to zero and the control bits for the cyclic shift for the DM RS is set to ‘000’.
 14. The user equipment of claim 11, wherein the UE-ID is a semi-persistent cell-radio network temporary identifier (C-RNTI). 